Although blends of isotactic polypropylene and olefin copolymers are well known in the prior art, prior art systems could not produce a good balance of flexural modulus, tensile strength and elasticity as a function of the content of the olefin copolymer. There exists a need for polymeric materials which have advantageous processing characteristics while still providing suitable end properties to articles formed therefrom. Copolymers and blends of polymers have been developed to try and meet the above needs. The present invention shows a surprising and unexpected balance of flexural modulus, tensile strength and elasticity as a function of the content of the alpha olefin. Moreover, these and other properties of the copolymers show surprising differences relative to conventional polymer blends, such as blends of isotactic polypropylene and propylene alpha olefin copolymers.
U.S. Pat. No. 4,178,272 describes hot-melt adhesives comprising a thermally degraded crystalline polypropylene, a propylene/hexene copolymer and a hydrocarbon resin.
U.S. Pat. No. 6,747,114 describes an adhesive composition that can include a semi-crystalline, preferably random, copolymer of propylene and at least one comonomer selected from the group consisting of ethylene and at least one C4 to C20 α-olefin.
U.S. Pat. No. 6,635,715 describes thermoplastic polymer blend compositions comprising an isotactic polypropylene component and an α-olefin/propylene copolymer component, said copolymer comprising crystallizable α-olefin sequences.